EP-B1-0473587 concerns a method for manufacturing of an improved hull, primarily for ships and boats, in particular with regards to surface finish, heat insulation and acoustic absorption. According to this known method sheets of cellular plastic is glued on to the outer surface of the hull.
In mounting of the sheets of cellular plastic or other light weight material on the hull the quality of the glue joint is of the highest importance to ensure the hull systems function in long term use, which could be 30-50 years. On a surface on the inner hull of for example metal, plastic or concrete, or alternatively directly on the sheets according to a preferred method, a film of elastic or viscoelastic glue is first applied, which is evened out to an evenly distributed layer.
In mounting of the sheets of cellular plastic or other light weight material it is necessary to create an even vacuum over the sheets for evacuation of the air from the glue joint between the hull and the sheets for eliminating the presence of air pockets. The problem has been to achieve a glue joint that is guaranteed to be free from air pockets, which otherwise creates uncertainty of the quality and strength of the construction during the many years of use. In conventional vacuum gluing for example a sheet and an intermediate glue layer is pressed against another surface, through that an impermeable foil with one or more vacuum valves is placed over the sheet and is taped up in the sides, whereafter a negative pressure is brought on. Thereby the foil and the sheet is sucked/pressed against the surface to which the sheet shall be glued with a pressure of up to 1 Kg/cm2. However it has been shown that air pockets can arise in the glue joint in such conventional vacuum gluing, especially if the surface is uneven. For making the manufacturing process and the assembly work run efficiently it is preferable that control and monitoring of the gluing step can be made visually. The problem is hence that in the gluing process, to as large extent as possible, eliminate the arising of air pockets and develop a method enabling, with visual control only, to determine that the glue between the two surfaces which should be glued fully fills the space and that the space thereby is entirely free from air pockets.
In particular it is a large problem to create good adherence when mounting of sheets of cellular plastic on to metal hulls, since the metal hull usually has a considerably more uneven surface in comparison to sandwich constructions in plastic, concrete etc.